Law enforcement advisory that Silk Road marketplace has been shut down.

San Francisco’s Glen Park public library doesn’t much resemble Chicago’s Biograph Theater. If you’re not steeped in the lore of Depression-era crime, the Biograph is the North Side movie house where bank robber John Dillinger met his end in a hail of FBI gunfire. The library branch in Glen Park is not pockmarked from a recent fusillade, but it shares something else with the Biograph: It’s where the FBI took down a patron accused of being the mastermind of “Silk Road,” an international online narcotics marketplace.

Paul Elias of the Associated Press recounts what happened when agents confronted their target in the library’s science fiction section:

The man known as Dread Pirate Roberts — 29-year-old Ross William Ulbricht — was on his personal laptop Tuesday afternoon, authorities said, talking about the vast black market bazaar that is believed to have brokered more than $1 billion in transactions for illegal drugs and services.

When a half-dozen FBI agents burst into the library in a quiet, blue-collar neighborhood, they abruptly ended Ulbricht’s conversation with a cooperating witness, pinned the Austin, Texas, native to a floor-to-ceiling window and then took him off to jail, law enforcement and library spokeswomen said.

Ever since the feds announced Ulbricht’s arrest yesterday — and unsealed federal criminal complaints against him in New York and Maryland — the web has been awash in stories about Silk Road and the newly unmasked Dread Pirate Roberts. The complaints say Ulbricht engineered Silk Road as a global drug marketplace, plotted to use the Bitcoin alternative currency system to facilitate narcotics transactions and tried to arrange a contract killing. Ulbricht’s take from Silk Road is alleged to have been in the millions of dollars.

As the AP reports, “Ulbricht has not entered pleas to any of his charges. His federal public defender in San Francisco declined to comment Wednesday. Ulbricht is due back in San Francisco federal court Friday morning to discuss bail and his transfer to New York, where the bulk of the charges have been filed.”

The case is fascinating on many levels, but maybe the most absorbing thing is that the Penn State engineer-turned-alleged crime lord left such suggestive traces of his life online, including a LinkedIn profile featuring a smiling, well-scrubbed Ulbricht. In fact, we really like what Business Insider did in the hours after the Silk Road arrest was announced. The site mined Ulbricht’s social network for a “biography”: Meet Ross Ulbricht, the Brilliant Alleged Mastermind of Silk Road.